Ever since Rick Santorum ended his presidential campaign a year ago this week, he has acted as if that defeat was just a brief setback in his running quest for the Republican nomination.

Almost three years out from the 2016 Iowa caucuses, the former Pennsylvania senator is set to return Monday to the nation’s first voting state, where he won a come-from-behind battle against Mitt Romney by 34 votes in January 2012.

Having witnessed the perils of underestimating him, Santorum’s potential rivals next time around aren’t likely to discount another strong challenge on his part, particularly in the Hawkeye State.

But well before the 2016 GOP field begins to take shape, Santorum’s paramount political priority is to push back against the winds of change within the party. In particular, he’s focused on a de-emphasis -- and in some cases an evolution -- of stances on social issues in order to attract more moderate voters in general elections and acknowledge shifts in the broader electorate’s views.

In an interview with the Des Moines Register this week that set the stage for his upcoming visit, Santorum was asked about the recent avowals of support for gay marriage made by Republican Sens. Rob Portman of Ohio and Mark Kirk of Illinois.

Santorum dismissed the growing notion that further movement within the GOP on the issue is inevitable, given polls showing a majority of Americans now support same-sex marriage.

“The Republican Party’s not going to change on this issue,” he said. “In my opinion, it would be suicidal if it did.”

The main event during Santorum’s impending return to Iowa will be his keynote speech in Urbandale at the annual spring fundraising dinner for the Iowa Faith & Freedom Coalition, a Christian conservative group that holds deep influence among evangelical caucus-goers in the state. He also is slated to participate in a Des Moines luncheon on behalf of a pro-life medical research group.

In both appearances, Santorum is expected to defend what he has called the “soul of the Republican Party” against forces within it that are increasingly eager to downplay or reconsider longstanding aspects of its platform.

His eagerness to remain on the front lines of this intra-party fight comes after Santorum spent much of the 2012 campaign defending his hard-line positions on social issues while also aiming to expand his appeal by touting his blue-collar credentials and economic populism.

“We’d go a whole day in Iowa talking about the economy, his manufacturing plan, and lowering taxes, and then at the last minute a reporter would come up to him and say, ‘Hey, what do you think about gay marriage?’ ” recalled Hogan Gidley, who served as Santorum’s traveling spokesperson during the 2012 campaign. “And we used to laugh at that because a lot of times he wouldn’t even bring it up.”

But the forums for his two Iowa appearances on Monday suggest that Santorum is intent on reminding the conservative wing of the state GOP of his long history and continued identity as a passionate, true-believing fighter on hot-button topics like gay marriage and abortion.

“That’s who he is and what he believes in,” Gidley said. “Santorum is not shy or unwilling to talk about social issues. Mitt Romney ran the campaign he wanted to run: It was all about the economy, but Santorum has often said if you’re not on the offense on social issues, you’re on the defense.”

His return to Iowa so long before the next presidential contest is apparently part of an aggressive effort to defend his territory there as a new generation of Republicans with White House ambitions soaks up considerable attention with their own early maneuverings.

Florida Sen. Marco Rubio waited less than two weeks after Election Day to make an appearance in the state, and Kentucky Sen. Rand Paul is slated to headline an Iowa Republican Party fundraising dinner next month. Meanwhile, CNN reported on Thursday that Louisiana Gov. Bobby Jindal is heading to the first-in-the-nation primary state of New Hampshire for a fundraiser next month.

All of these movements make it particularly important for Santorum to remain in the limelight in Iowa.

“If he were to jump in again in 2016, he’d really have to win Iowa again,” said one Republican strategist, who remains close to the two-term former senator’s political orbit. “You can debate what he’d do in New Hampshire and on, but the fight for the base in Iowa is really going to be important. You really have to have a niche, and that’s why he’s going out there so strongly, and that’s why he’s being vocal about it.”

Though his focus for the time being is on social issues, Santorum has spoken at characteristic length on a wide range of topics during his frequent speeches around the country. He delivered a fiery foreign policy speech at Johns Hopkins University earlier this week, for instance, in which he accused President Obama of “appeasing” Iran.

Santorum is heading to a Michigan high school later this month after a dispute surrounding his appearance there led officials to cancel it -- before deciding to reinstate the visit on the condition that students have parental permission to attend.

The controversy was a reminder of the extent to which Santorum can inflame passions among both supporters and detractors.

But just five months after the last presidential election, even some of Iowa’s famously politically obsessed activists aren’t especially eager to dive back into the fray.

“It's too early in the cycle for me to toss my hat in anybody's ring,” said Madison County Republican Party Chairman Joe Van Ginkel, who doesn’t plan to attend either of Santorum’s speeches. “I'm really enjoying the slow politics season right now and still trying to recover from the last election.”

But in the effort to build and sustain his 2016 hopes, there can be no slow season for Santorum: Later this month, he will head to the first-in-the-South primary state of South Carolina where he will speak at a pregnancy center in Spartanburg.